The present invention relates to a writing instrument, and particularly to a writing instrument in which the tip of a writing element such as a writing lead is projected and withdrawn by operating a knock member at the rear end of the writing instrument to enable writing.
In the conventional rear-end knock type writing instrument of this kind, an internal mechanism provided with a writing element at the tip thereof relative to a barrel can be slidably moved by operation of a knock member. Therefore, there is formed a clearance between the knock member and the barrel in terms of construction.
Further, also in a writing instrument in which at the rear end of a barrel, a tail crown is mounted by threaded engagement with the barrel, and a knock member is slidably moved within the tail crown, there is likewise formed a clearance between the knock member and the tail crown.
As a result, the knock member rattles or rotates during the knocking operation due to the presence of the clearance to make it difficult to carry out the knocking operation positively. Further, in the case of a metallic knock member, the knock member freely moves vertically due to vibration produced in carrying and collides with other members to produce an unpleasing sound, "clattering".
In particular, in a double chuck type mechanical pencil, the rattle or rotation of the knock member is transmitted to a rear chuck for drawing out a lead so that the lead held between the front chuck and the rear chuck is sometimes twisted and broken.